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Viagra History: Discovery Timeline
1989
- Pfizer Scientists synthesize silendafil citrate and give it the code name UK-92, 480. The drug would not be known as Viagra until the mid-90s.
- Experimental compound UK-92,480 is believed to be useful as a high blood pressure and angina treatment. The scientists hope it may act as a vasodilator and be useful in treating cardiovascular ailments such as hypertension and angina.
1991
- Researchers at Pfizer’s Sandwich, England research facility (Peter Ellis and Nick Terret) observe that drugs that inhibit the PDE5 enzyme may be helpful in reversing erectile dysfunction.
- Early Phase 1 trials regarding the use of Viagra for angina are unremarkable.
1992
- A second Phase 1 angina trial reveals that the drug has an unusual side effect; penile erections.
- Phase 2 clinical study is conducted testing silendafil citrate’s usefulness as an angina treatment.
1993
- Pilot study using silendafil citrate as a treatment for erectile dysfunction is conducted in Bristol, England. Test subjects take it three times a day for a week. The studies had only 28 men involved.
1994
- Second pilot study on silendafil as an Erectile dysfunction treatment demonstrates that a once per day dose is able to produce an erection.
- Pfizer realizes it has something important; it accelerates the program examining silendafil citrate for erectile dysfunction.
1994 – 1997
- 21 clinical trials are conducted involving 4,500 men demonstrate that Viagra (as it is now known) is safe and effective.
1997
- Pfizer files a New Drug Application for Viagra (NDA 020895) with the United States FDA. FDA agrees to give it a priority review.
1998
- FDA approves Viagra as the first oral treatment for erectile dysfunction. It was approved with a starting dose of 50 mg with the option to increase the dose to 100mg or reduce it to 25 mg.
Misc:
- FDA lists two patents for Viagra. Patent number 5250534 expires on March 27, 2012. Patent number 6469012 (patent use code U-155; TREATMENT OF ERECTILE DYSFUNCTION) is set to expire on Oct 22, 2019.
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